metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; white, gray, or pinkish color; vitreous to greasy luster; non-foliated crystal structure; conchoidal fracture with no true cleavage; specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; white, gray, or pinkish color; vitreous to greasy luster; non-foliated crystal structure; conchoidal fracture with no true cleavage; specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone subjected to high temperatures and pressures during regional or contact metamorphism, typically during mountain-building events over millions of years.
Uses & applications
Used in construction, road aggregate, manufacturing of silica bricks, railroad ballast, and occasionally for decorative stone and countertops.
Geological facts
Quartzite is extremely durable and weather-resistant, which is why ridges made of quartzite often form prominent hills or mountain crests as the surrounding softer rock erodes away.
Field identification & locations
Identified in the field by its hardness (scratches glass easily), sugary texture on freshly broken surfaces, and lack of reaction to dilute hydrochloric acid. Commonly found in mountainous regions worldwide.
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